When the exact resemblance of our perceptions makes us ascribe to them an identity, we may remove the seeming interruption by feigning a continued being, which may fill those intervals, and preserve a perfect and entire identity to our perceptions.
But as we here not only feign but believe this continued existence, the question is, from whence arises such a belief; and this question leads us to the fourth member of this system.

It has been proved already, that belief in general consists in nothing, but the vivacity of an idea; and that an idea may acquire this vivacity by its relation to some present impression.

Impressions are naturally the most vivid perceptions of the mind; and this quality is in part conveyed by the relation to every connected idea.

The relation causes a smooth passage from the impression to the idea, and even gives a propensity to that passage.

The mind falls so easily from the one perception to the other, that it scarce perceives the change, but retains in the second a considerable share of the vivacity of the first.